Abstract: A quantum cascade detector includes a semiconductor substrate, and an active layer formed by laminating unit laminate structures each having an absorption region with a first barrier layer to a second well layer and a transport region with a third barrier layer to an n-th well layer. A second absorption well layer has a layer thickness ½ or less of that of a first absorption well layer thickest in one period, and a coupling barrier layer has a layer thickness smaller than that of an exit barrier layer thickest in one period. The unit laminate structure has a detection lower level arising from a ground level in the first well layer, a detection upper level generated by coupling an excitation level in the first well layer and a ground level in the second well layer, and a transport level structure for electrons.

Abstract: A quantum cascade laser includes a semiconductor substrate, and an active layer that is provided on the substrate, and has a cascade structure in which emission layers and injection layers are alternately laminated by multistage-laminating unit laminate structures each consisting of the quantum well emission layer and the injection layer, the active layer generates light by intersubband transition in a quantum well structure. Further, in a laser cavity structure for light with a predetermined wavelength to be generated in the active layer, reflection control films including at least one layer of CeO2 film are formed on a first end face and a second end face facing each other. Thereby, it is possible to realize a quantum cascade laser capable of preferably realizing reflectance control for light within a mid-infrared wavelength region on the laser device end face.

Abstract: A quantum cascade laser includes a semiconductor substrate, and an active layer that is provided on the substrate, and has a cascade structure in which emission layers and injection layers are alternately laminated by multistage-laminating unit laminate structures each consisting of the quantum well emission layer and the injection layer, and generates light by intersubband transition in a quantum well structure. Further, in a laser cavity structure for light with a predetermined wavelength to be generated in the active layer, CeO2 insulating films and reflection control films are formed in order on respective faces of a first end face and a second end face facing each other. Thereby, it is possible to realize a quantum cascade laser capable of preferably realizing reflectance control for light within a mid-infrared region on the laser device end face.

Abstract: A quantum cascade detector includes a semiconductor substrate, and an active layer formed by laminating unit laminate structures each having an absorption region with a first barrier layer to a second well layer and a transport region with a third barrier layer to an n-th well layer. A second absorption well layer has a layer thickness ½ or less of that of a first absorption well layer thickest in one period, and a coupling barrier layer has a layer thickness smaller than that of an exit barrier layer thickest in one period. The unit laminate structure has a detection lower level arising from a ground level in the first well layer, a detection upper level generated by coupling an excitation level in the first well layer and a ground level in the second well layer, and a transport level structure for electrons.

Abstract: A quantum cascade laser includes a semiconductor substrate, and an active layer being provided on the substrate, and having a cascade structure in which quantum well emission layers and injection layers are alternately laminated, and the laser has a base portion including the substrate, and a stripe-shaped ridge portion including the active layer. Further, a reflection control film is formed from a ridge end face over a base end face on an end face in a resonating direction of the laser, and, on the base end face, for a second side and a third side adjacent to a first side on the ridge portion side of the base end face, and a fourth side facing the first side, the reflection control film is formed on a region other than regions near those three sides with predetermined widths.

Abstract: A quantum cascade laser 1 includes a semiconductor substrate, an active layer 15 that is disposed on the semiconductor substrate and has a cascade structure in which a unit layered structure 16 including a quantum well light emitting layer and an injection layer is stacked in multiples to alternately stack the quantum well light emitting layer and the injection layer, and a diffraction grating layer 20 disposed on the active layer.

Abstract: A quantum cascade laser 1 includes a semiconductor substrate, an active layer 15 that is disposed on the semiconductor substrate and has a cascade structure in which a unit layered structure 16 including a quantum well light emitting layer and an injection layer is stacked in multiples to alternately stack the quantum well light emitting layer and the injection layer, and a diffraction grating layer 20 disposed on the active layer.

Abstract: A quantum cascade laser manufacturing method includes: a step of pressing a mother stamper against a resin film having flexibility to make a resin stamper 201 having a second groove pattern P2; a step of making a wafer with an active layer formed on a semiconductor substrate; a step of forming a resist film 304 on a surface on the active layer side of the wafer; a step of pressing the resin stamper against the resist film 304 by air pressure to form a third groove pattern P3 on the resist film 304; and a step of etching the wafer with the resist film 304 serving as a mask to form a diffraction grating on a surface of the wafer.

Abstract: A quantum cascade laser is configured to include a semiconductor substrate, and an active layer that is provided on the substrate and has a cascade structure formed by alternately laminating emission layers and injection layers by multistage-laminating unit laminate structures each consisting of the quantum well emission layer and the injection layer, and generates light by intersubband transition in a quantum well structure. In a laser cavity structure for light with a predetermined wavelength generated in the active layer, a front reflection film with a reflectance of not less than 40% and not more than 99% for laser oscillation light is formed on the front end face that becomes a laser beam output surface, and a back reflection film with a reflectance higher than that of the front reflection film for the laser oscillation light is formed on the back end face.

Abstract: A laser module LM is provided with a quantum cascade laser 1, a tubular member 5, and an infrared detector 7. The tubular member 5 has a pair of opening ends 5a, 5b and is arranged so that one opening end 5a is opposed to a face 1b opposed to an emitting end face 1a of the quantum cascade laser 1. The infrared detector 7 is arranged so as to be opposed to the other opening end 5b of the tubular member 5. Light emitted from the face (rear end face) 1b opposed to the emitting end face (front end face) 1a of the quantum cascade laser 1 is guided inside the tubular member 5 to enter the infrared detector 7, and then is detected.

Abstract: A quantum cascade laser is configured to include a semiconductor substrate and an active layer which is provided on the substrate and has a cascade structure formed by multistage-laminating unit laminate structures 16 each including an emission layer 17 and an injection layer 18. The unit laminate structure 16 has, in its subband level structure, a first emission upper level Lup1, a second emission upper level Lup2 of an energy higher than the first emission upper level, an emission lower level Llow, and a relaxation level Lr of an energy lower than the emission lower level, light is generated by intersubband transitions of electrons from the first and second upper levels to the lower level, and electrons after the intersubband transitions are relaxed from the lower level to the relaxation level and injected from the injection layer 18 into an emission layer 17b of a subsequent stage via the relaxation level.

Abstract: A dental therapy apparatus which enables a dental therapy more surely and less invasively is provided. A dental therapy apparatus (10A) comprises a laser light source (11) emitting laser light (L) having a wavelength within a wavelength region of 5.7 to 6.6 ?m; a controller (12) pulse-driving the laser light source and controlling at least one of pulse width and repetition frequency of pulsed laser light emitted from the laser light source; and an irradiation optical system for irradiating a tooth (20) including a carious part (21) with the light emitted from the laser light source. In this dental therapy apparatus, the controller controls at least one of the pulse width and repetition frequency of the pulsed light, so as to selectively cut the carious part (21).

Abstract: A quantum cascade laser includes a semiconductor substrate, and an active layer that is provided on the substrate, and has a cascade structure in which emission layers and injection layers are alternately laminated by multistage-laminating unit laminate structures each consisting of the quantum well emission layer and the injection layer, the active layer generates light by intersubband transition in a quantum well structure. Further, in a laser cavity structure for light with a predetermined wavelength to be generated in the active layer, reflection control films including at least one layer of CeO2 film are formed on a first end face and a second end face facing each other. Thereby, it is possible to realize a quantum cascade laser capable of preferably realizing reflectance control for light within a mid-infrared wavelength region on the laser device end face.

Abstract: A quantum cascade laser includes a semiconductor substrate, and an active layer that is provided on the substrate, and has a cascade structure in which emission layers and injection layers are alternately laminated by multistage-laminating unit laminate structures each consisting of the quantum well emission layer and the injection layer, and generates light by intersubband transition in a quantum well structure. Further, in a laser cavity structure for light with a predetermined wavelength to be generated in the active layer, CeO2 insulating films and reflection control films are formed in order on respective faces of a first end face and a second end face facing each other. Thereby, it is possible to realize a quantum cascade laser capable of preferably realizing reflectance control for light within a mid-infrared region on the laser device end face.

Abstract: A wavelength-tunable light source includes a quantum cascade laser that emits light from a first end and a second end, an optical system that collimates the light emitted from the first end, a first reflecting section on which the light collimated by the optical system is made incident, and a second reflecting section that partially reflects the light emitted from the second end of the quantum cascade laser and transmits the remaining light. The first reflecting section includes a plurality of diffractive gratings whose diffractive properties are different from each other and whose lattice plane directions are variable, and the first reflecting section diffracts a light at a particular wavelength corresponding to the diffractive property and the lattice plane direction of the selected diffractive grating in the direction opposite to the incident direction.

Abstract: A quantum cascade laser includes a semiconductor substrate, and an active layer having a cascade structure formed by multistage-laminating unit laminate structures each including an emission layer and an injection layer. Further, the unit laminate structure 16 includes a first emission upper level, a second emission upper level, and a plurality of emission lower levels, one of the first and second upper levels is a level arising from a ground level in the first well layer, and the other is a level arising from an excitation level in the well layer except for the first well layer. Further, the energy interval between the first upper level and the second upper level is set smaller than the energy of an LO phonon, and the energy interval between the second upper level and a higher energy level is set larger than the energy of an LO phonon.

Abstract: A quantum cascade laser is configured so as to include a semiconductor substrate and an active layer which is provided on the substrate and has a cascade structure including multistage-laminated unit laminate structures each including a quantum well emission layer and an injection layer. Moreover, the unit laminate structure has, in its subband level structure, an emission upper level, a lower level, and an injection level 4 of higher energy than the upper level, and light h? is generated by intersubband transition of electrons from the level to the level in the emission layer, and electrons after emission transition are injected into the injection level 4 of the subsequent stage via the injection layer. In addition, the emission layer includes two or more well layers, and the first well layer closest to the injection layer of the preceding stage is used as a well layer for injection level formation.

Abstract: A semiconductor light emitting device including a semiconductor substrate and an active layer which is formed on the substrate and has a cascade structure formed by multistage-laminating unit laminate structures 16 each including an emission layer 17 and an injection layer 18 is configured. The unit laminate structure 16 has a first upper level L3, a second upper level L4, and a lower level L2 in the emission layer 17, and an injection level L1 in the injection layer 18, an energy interval between the levels L3 and L4 is set to be smaller than the energy of an LO phonon, the layer thickness of the exit barrier layer is set in a range not less than 70% and not more than 150% of the layer thickness of the injection barrier layer, light is generated by emission transition in the emission layer 17, and electrons after the emission transition are injected from the level L2 into the level L4 of the emission layer of a subsequent stage via the level L1.

Abstract: A wavelength-tunable light source includes a quantum cascade laser that emits light from a first end and a second end, an optical system that collimates the light emitted from the first end, a first reflecting section on which the light collimated by the optical system is made incident, and a second reflecting section that partially reflects the light emitted from the second end of the quantum cascade laser and transmits the remaining light. The first reflecting section includes a plurality of diffractive gratings whose diffractive properties are different from each other and whose lattice plane directions are variable, and the first reflecting section diffracts a light at a particular wavelength corresponding to the diffractive property and the lattice plane direction of the selected diffractive grating in the direction opposite to the incident direction.

Abstract: A quantum cascade laser is configured to include a semiconductor substrate, and an active layer that is provided on the substrate and has a cascade structure formed by alternately laminating emission layers and injection layers by multistage-laminating unit laminate structures each consisting of the quantum well emission layer and the injection layer, and generates light by intersubband transition in a quantum well structure. In a laser cavity structure for light with a predetermined wavelength generated in the active layer, a front reflection film with a reflectance of not less than 40% and not more than 99% for laser oscillation light is formed on the front end face that becomes a laser beam output surface, and a back reflection film with a reflectance higher than that of the front reflection film for the laser oscillation light is formed on the back end face.